1. Field of the Invention
The present invention relates to a transparent coordinate input device for directly inputting coordinates on a screen, and a transparent composite material constituting this transparent coordinate input device.
2. Description of the Related Art
A portable information terminal represented by PDA generally has a coordinate input device for selecting a menu and inputting data by directly operating the display screen such as a liquid crystal display panel, etc. by a pen, a finger, etc. Such a coordinate input device normally has a transparent coordinate input device formed on the liquid crystal display panel and the data is inputted by indicating the display of the liquid crystal display panel. As is well known, the transparent coordinate input device of a resistance film type particularly widely used among the transparent coordinate input device has a glass plate forming a transparent resistance film called ITO (Indium Tin Oxide) on its surface on the liquid crystal display panel side, and a soft transparent resin film such as PET (polyethylene terephthalate film), etc. forming a similar transparent resistance film on its surface on the operation side. This transparent coordinate input device is a flat panel device made by spacing these two transparent resistance films from each other by an insulating spacer, etc., and oppositely arranging these two transparent resistance films.
When an input operation is performed by pressing the surface of the transparent coordinate input device by a pen or a finger in such a transparent coordinate input device, it is known that the transparent resin film on the operation side is slightly recessed and a rainbow-colored annular interference fringe is generated with the pressing portion as a center. When such an interference fringe is generated, visibility of the liquid crystal display panel is reduced during every operation of the transparent coordinate input device so that it is difficult to perform a smooth and comfortable input operation. Such an interference fringe is particularly notably generated as the size of the transparent coordinate input device is increased. Therefore, an interference fringe countermeasure has been strongly desired due to the increase in the display screen size of the recent portable information terminal.
In consideration of the above present situation, a transparent coordinate input device having many fine projections formed on the surface of the transparent resistance film on the liquid crystal display panel side or the operation side is known as the conventional interference fringe countermeasure in the transparent coordinate input device. In such a transparent coordinate input device, light for illuminating the liquid crystal display panel is diffused in many directions by the fine projections formed on the surface of the transparent resistance film so that the generation of the interference fringe is restrained. (For example, see Patent Literature 1.)
[Patent Literature 1]
Japanese Unexamined Published Patent Application No. H8-281856
However, in the transparent coordinate input device having many fine projections formed on the surface of the transparent resistance film on the liquid crystal display panel side or the operation side as mentioned above, the individual projections respectively play the role of a microscopic lens so that many bright spots are formed by the display light of the liquid crystal display panel. Therefore, a problem exists in that the display is glittered when the liquid crystal display panel is seen from the outside of the transparent coordinate input device. Further, a problem also exists in that the liquid crystal display panel cannot be clearly observed and is defocused by the lens effect of the individual projections. Such glittering and defocusing due to the conventional transparent coordinate input device caused a reduction in the visibility of the liquid crystal display panel.